Semiautomatic motor-driven lens focusing mechanism



D United States Patent [111 3533330 [72] Inventors Elmer C. l-lenrlksen[56] References Cited Chicago, and UNITED STATES PATENTS [211 App No sggMwnm" View 1,301,897 4/1919 Becker 95 44 3,450,0l8 6 1969 J h 95 45 22Filed June 7, 1968 [45] Patented Nov. 10, 1970 Primary Examiner-John M.Horan [73] Assjgnee Bell 8; Howell Company Assistant ExaminerM. L.Gellner hi Illi i Attorneys-William F, Pinsak and John E. Peele, Jr. acorporation of Illinois ABSTRACT: A distance determining mechanism for acamera having a focusabie objective, the mechanism including a pendulousmember mounted for orientation by gravity to cause adjustment of theobjective into focus on a remote subject. [54] g gn2ZE Qg LENS Thedistance is determined by triangulation based on orienta- N 3 D i tionto an angular aspect of the pendulous member upon align- 10 C raw mentof the axis of the objective at the base of the remote sub- [52] US. Cl95/44, ject. The objective is adjusted by a motor for a time deter-95/45: 352/l40: 353/101 mined by a control circuit responding toorientation of the [5 1] Int. Cl G03b 13/20 pendulous member throughresistance variations as that [50] Field of Search 95/44, 45; member isoriented relative to a resistive element in the control circuit.

Patented Nov. 10, 1970 60 L @ob Elmer C. Henrikser;

rP bm B5 f lk SEMIAUTOMATIC MOTOR-DRIVEN LENS FOCUSING MECHANISM Thepresent invention relates to a camera focusing mechanism, andparticularly to a mechanism for adjusting a focusable lens of a camerain response to focal distances determined by a rangefmding devicefunctioning on the principle of triangulation. The lens is adjusted by amotor in a control circuitresponsive to the orientation of a gravityinfluenced member.

The triangulation principle relates to the computation of the length ofone side of a right triangle, herein the camera-to-subject distance. Tocompute the distance, the height of either the vertical side or thelength of the hypotenuse of the triangle, and one of the angles otherthan the right angle must be known. For use of the principle in a camerafocusing arrangement, the length of the vertical side of the trianglemay be empirically determined as the height of an average adult abovethe supporting plane on which the user stands. Thus, the vertical sidewill be approximately the same in most uses to which a camera is put. Byhaving the user align the base of a remote subject with a reference markin the viewfinder of the camera, the camera is caused to be angled bydeterminable amounts. That is, the user views the subject at the pointwhere a vertical line through the subject intersects the supportingplane. The optical axis of the camera's lens may be repeatably angled ata given angle relative to both the vertical side and the base side ofthe triangle. Hence, the required values necessary to compute theunknown length of the base line are available.

The present invention seeks to eliminate the need for mathematicalcomputation by the user by providing a mechanism which functions tofocus the lens on a semiautomatic basis. To determine the angle ofinclination of the optical axis, a pendulous member orientable under theinfluence of gravity is arranged to pivot about an axle which extendsperpendicularly of the optical axis. When the user sights the base of asubject at infinity, the optical axis remains horizontal with a baseline on which both the subject and the user are supported. Hence, thependulous member remains vertical and therefore perpendicular to thehorizontally oriented optical axis. However, if the user sights the baseof a near subject, the optical axis and camera housing will be inclinedrelative to the horizontal base line. As the housing is inclined, thependulous member, if free, will remain fixed in space continuing to hangvertically under the influence of gravity. In this orientation, thependulous member is understood to be displaced from the optical axis bya given angle. Since the range of angular displacements corresponding tothe range of focus planes of the lens can be determined, these valuesmay be built into a focusing mechanism to adjust the focus of the lensfor that given distance.

Translation of the angular orientation of a pendulous member to focusdistance for adjustment of the focus plane of a lens may be accomplishedthrough mechanical and electromechanical mechanisms. A mechanism foundto be advantageous is of the latter category in which the pendulousmember is an electric contact swinging relative to a resistive element.In response to variations of a resistance introduced in a motor controlcircuit by different positions of the contact on the element, a motor isenergized to focus the lens on a subject. The circuit developed employsrelatively inexpensive components interconnected in a relatively simplemanner. The particular circuit energizes the motor, times the durationduring which the motor is energized, and deenergizes the motor at theprecise moment required. Thus, it can be'seen that to focus a lens bythe system of this invention, the user need only view the base of asubject, and actuate a control.

The camera may subsequently be righted for framing of a scene, and thecamera operating button pushed.

Prior focusing and rangefinding systems for cameras or other opticalinstruments have generally required manual operation by the user. Mostof these systems have been of the short base variety in which theangle-defining component is within a few inches of the reference baseline relative to which the angle is determined. The short base islimited by the size of the instruments housing. Hence, extremelyaccurate and rela- Yet another object of the invention is to provide adistance determining mechanism for use with an instrument having afocusable objective, the objective being focused by power.

Further and other objects will be apparent from the descrip-- tion ofthe accompanying drawings in which like numerals refer to like'parts.

In the drawings:

FIG. 1 is a schematic and perspective view of an optical instrumentincorporating the focusing mechanism of this invention; J.

FIG. 2 is a schematic diagram of the circuitry associated,

with the present focusing mechanism; and

FIG. 3 is a schematic diagram in perspective disclosing ele-- ments ofthe focusing mechanism.

Referring to FIG. 1, there is shown an optical instrument such as camera10, comprising a housing having front wall 12 for supporting a focusableobjective or lens assembly 14, in lens barrel l6, and rear wall 18including opening 20 through which a user may view the image of remotesubject 24. Subject 24, shown schematically as a line, is focused bylens 14 onto an image plane (not shown). For different camera-to-subjectdistances, the focal plane of lens 14 must be varied to bring that planeinto coincidence with the image plane. A focusing lens cell, shown aselement 26, is made adjustable in a direction parallel with optical axis28 to vary the focal plane. In this exemplary disclosure, a motivemeans, shown as small motor 30, is operably connected to focusing lenscell 26 to reciprocate the same along optical axis 28.

The viewing system comprises first and second image reflecting devices,shown as mirrors 34, 36 for directing the image toward opening 20. Inthe viewing system and arranged to be visible therein is a referencemark 38 relative to which the image of the subject may be positioned fordetermining the distance to the instrument. When the instrument isoriented to align the point of intersection of a vertical line throughthe subject and a base plane common to the subject and user, opticalaxis 28 of lens 14 defines the hypotenuse of a triangle by use of whichthe length of the base line between the instrument and the subject canbe determined.

The distance determining mechanism includes pendulous member 50 mountedfor rotation about axis 52 which extends in a plane with, butperpendicular to the optical axis. As schematically represented in FIG.2, one end of the pendulous member moves as a wiper across resistiveelement 54 as pendulous member 50 is oriented swingably under theinfluence of gravity. In all of the positions of this swingable memberor wiper against the resistive element, a different resistance isintroduced into an electric circuit to ultimately focus objective lens14.

Pendulous member 50 and resistive element 54 are connected to a controlcircuit shown schematically in FIG. 2. The circuit in which motor 30 isalso connected, includes controlled power supply 58 comprising a powersource such as battery 62, fixed resistance 64 in series with thebattery, and zener diode 66 in parallel with the battery. The dioderegulates the voltage output of the battery wherein a constant voltageis introduced to the balance of the circuit. By conductor 68, one sideof power supply 58 is connected to either wiper 50 or to resistiveelement 54. In this preferred embodiment, the wiper is connected byconductor 72 to the other side of the supply through timing network orcircuit 70.

The timing circuit functions to control the length of time during whichthe objective is driven for focusing. Timing circuit 70 includesadjustable resistance 74, which remains fixed after a preliminary orfactory adjustment to accommodate the circuit for variations in otheraspects of the objective focusing system. The circuit also includescapacitor 78 which receives current in varying quantities as controlledby the adjusted resistance and resistive element 54. By the varyingquantities of current fed into the capacitor, it is charged to a givenpercentage of capacity at varying rates. The rate of charge is primarilyvaried by the position of wiper 50 on resistive element 54, whichcreates a high resistance when the wiper is near the lower end asoriented in FIG. 2, and a low resistance when the wiper is near theupper end. The charging times of the capacitor are thus seen to berelatively long and short, respectively, as the current flow thereto isaltered.

Current flow from power supply 58 to the balance of the circuit and themotor is initiated upon manual closure of normally open switch 80. Theswitch includes a pair of contact sets 80a, 80b shown physicallyseparated, but mechanically interlocked for simultaneous actuation. Uponclosure of switch 80, full voltage is fed from power supply 58 to motoramplifier and switch circuit 84. This circuit in turn energizes themotor to full on". As the motor is energized, the other contact set ofswitch 80 also closes to initiate current flow into timing circuit 70,and thereby initiates the timing period during which the motor isoperated.

After a quantity of voltage is fed from power supply 58 into timingcircuit 70 to charge capacitor 78, the capacitor discharges intounijunction transistor 88. The transistor, connected to the timingcircuit by conductor 90, is in series circuit with a pair of resistors92, 94 and conductor 96 connected to silicon controlled rectifier 100,which is in series with resistor 98. The lower resistor 92 is selectedof a value to determine the voltage to which capacitor 78 must becharged before discharging through transistor 88. Upon discharge ofcapacitor 78, a positive going trigger pulse is generated by thetransistor, and fed into conductor 96.

Conductor 96 connects transistor 88 to silicon controlled rectifier 100to cause that rectifier to be turned on in response to the triggerpulse. Before the SCR is triggered on, it is effectively ahigh-resistance element causing a relatively positive polarity currentflow into the motor amplifier which in turn permits operation of themotor. However, after the trigger pulse voltage is received by the SCRthe resistance through it drops, effectively turning it on. In turn, theSCR turns off the motor amplifier which deenergizes motor 30. When themotor is deenergized, lens 14 has been moved for a predetermined time inan axial direction to bring the image of a remote subject into focus onthe image plane in the camera.

Manually operable control member 110 is shown in FIG. 3 as a lever towhich other linkage members can be connected for actuation externally ofthe camera housing. Control member 110 is provided for resetting lens 14to a start position, and for actuating the distance determiningmechanism. Control member 110 is mounted for movement about pivot 116fixed interiorly of the housing of the camera. The end of member 110remote from pivot 116 extends through a slot (not shown) formed inmechanism plate 118. A plurality of detent portions 120 are formed inbent-over portion 124 of the plate to receive detent member 128 fixed tomember 110. Control member 110 is formed of slightly flexible andresilient material so that the detent member may be aligned with adetent portion and released to seat therein. The detent portions may bedesignated respectively from the top as on, off",

' and reset as oriented in FIG. 3.

The three positions of control member 110 serve to define the functionof the distance determining mechanism. In the central or off position,the member is spaced from a microswitch, representative of switch 80,which the member will engage adjacent one end of its throw, and isspaced from motor housing portion 130. The motor housing portion may beeither an extension from or an integral part of the housing of motor 30,from which extends drive shaft 132. Pinion 134 is fixed on the end ofdrive shaft 132 remote from motor 30. The pinion is selectively movableinto and out of mesh with drivable gear 138 about lens barrel 16, but isurged continuously toward mesh therewith by a biasing element, shown asspring 140. Hence, when the motor is energized, lens barrel 16 isrotated to reciprocatively position focusing lens cell 26.

After a focusing operation, activation of control member 1 10 to areset" position conditions lens 14 back to start for focusing at anotherdistance. Upon shifting the member from the off position, the memberengages motor housing extension portion to move the motor housing abouta pivot axis through shafts 142. This movement of the motor housingdisplaces pinion 134 from engagement with drivable gear 138 of the lensbarrel. With the lens barrel free of the restraining force of thepinion, a return member, shown as spring 146, returns the lens, andtherefore focusing cell, to start". The amount of rotation of the barrelis limited by stop 148 which is engaged by cooperating portion 150 onthe barrel, shown as the end of gear 138. The lens is thus conditionedfor a new focusing operation.

A focusing operation is initiated by movement of control member 110 tothe on or upper position. The initial movement from the reset positionpermits spring to cause reengagement of pinion 134 with drivable gear138. As the member approaches the on position, lug portion 154 engagesand closes switch 80, thereby energizing the focus control circuit andmotor 30. As earlier described, motor 30 drives for a predetermined timeto reciprocate focusing cell 26 into focus on the remote subject. Whenthe lens is focused, control member 110 is returned to the off"position. Since pinion 134 remains in mesh with gear 138, lens 14 willremain in focus at this distance until reset for focusing at anotherdistance.

it is to be understood that the embodiment shown is illustrative of theprincipal operation of a focusing mechanism for cameras which employ apendulous rangefinder, and that certain changes, alterations,modifications or substitutions can be made in the structure of themechanism without departing from the spirit and scope of the claims.

We claim:

1. In an optical instrument having a housing and a focusable objectivelens arranged from said housing for focusing adjustment, the combinationcomprising:

a pendulous member mounted for swinging movement relative to saidhousing to an angular aspect corresponding to focal distance; and

motive means responsive to the angular aspect of the pendulous memberfor driving said objective assembly toward a focused condition.

2. A combination as in claim 1 in which said motive means comprises amotor for driving said objective assembly and electrical meansresponsive to the angular aspect of said pendulous member for energizingsaid motor to adjust said objective assembly.

3. A combination as in claim 2 wherein said electrical means includescircuit breaking means for deenergizing said motor when said objectiveis in focused condition.

4. A distance determining device for an optical instrument having a lensfocusable on a remote subject at a distance defined by the inclinationof a pendulous member orientable perpendicular to the axis of theobjective wherein the axis defines the hypotenuse of a triangle and theinstrument-tosubject distance defines the base of the triangle, thedevice comprising:

lens adjusting drive means;

a control circuit energizeable simultaneously with said drive means tocontrol drive of the lens for focusing over a range of distances whilesaid circuit is energized; and

means in said control circuit responsive to the oriented position ofsaid pendulous member for deenergizing said drive means with said lensfocused on said subject.

5. The device as in claim 4 wherein said pendulous member is movablerelative to a fixedly located variable resistance element connected tovary said control circuit in response to different oriented positions ofsaid pendulous member.

6. The device as in claim 4 wherein said means in said control circuitresponsive to said oriented position of said pendulous member includes atiming network, the actuation of which initiates upon energization ofsaid circuit, and said timing network providing a preselected outputvoltage after a period of time determined by the position of saidpendulous member.

7. The device as in claim 6 wherein said timing network is aresistance-capacitance network.

8. The device of claim 7 wherein a unijunction transistor is connectedto a capacitor of said timing network wherein said transistor istriggered when the voltage across the capacitor reaches a predeterminedvalue.

9. The device of claim 4 wherein a control member is movable manually toa plurality of positions, one of said positions initiating energizationof said control circuit.

10. The device of claim 4 wherein a control member is movable manuallyto a plurality of positions, one of said positions conditions a focusedobjective to return to a start position for another focusing operation.

